The influence of placenta microbiota of normal term pregnant women on immune regulation during pregnancy.

BACKGROUND: The concerted regulation of placenta microbiota and the immune responses secures the occurrence and development of pregnancy, while few studies reported this correlation. This study aimed to explore the relationship between the placenta microbiota and immune regulation during pregnancy. METHODS: Twenty-six healthy pregnant women scheduled for elective cesarean section in the First Affiliated Hospital of Jinan University who met the inclusion criteria were recruited. Placenta and peripheral venous blood samples were collected. Microbiota in placental tissue was detected using high-throughput sequencing. Flow cytometry was used to detect immune cells in placental tissue and peripheral venous blood. ELISA and Luminex liquid chip technology were used to detect the content of cytokines in placental tissue and peripheral venous blood, respectively. RESULTS: The placental microbiota has stimulating effects on the local immunity of the placenta and mainly stimulates the placental balance ratio CD56 + CD16 + /CD56 + CD16 and the placental macrophages, that is, it plays the role of immune protection and supporting nutrition. The stimulating effect of placental microbiota on maternal systemic immunity mainly induces peripheral Treg cells and B lymphocytes. CONCLUSION: The placental microbiota may be an important factor mediating local immune regulation in the placenta, and placental microbiota participates in the regulatory function of the maternal immune system.

Direct access to carbamates via acylation of arylamines with dialkyl azodicarboxylates under metal-free conditions.

A novel C-N coupling of various arylamines with dialkyl azodicarboxylates under metal-free conditions for the rapid assembly of carbamates has been achieved. This established protocol features mild reaction conditions, simple operation, broad substrate scope, moderate to excellent yields and good tolerance of functional groups. Moreover, the potential synthetic utility of products was exemplified by a series of intriguing chemical operations.

Emotional bias modification weakens game-related compulsivity and reshapes frontostriatal pathways.

Addiction is characterized by compulsive engagement despite adverse consequences. Psychobehavioural interventions targeting compulsivity in addictions are relatively rare, particularly for behavioural addictions like internet gaming disorder (IGD). Free from confounding drug-on-brain effects, IGD provides a promising model for understanding neuropsychological processes of addictions. IGD is a global concern in the setting of increasing internet use worldwide. Thus, developing interventions and understanding their mechanisms of action are important. Positive emotional association biases (EABs) towards addiction cues based on reward conditioning may underlie addiction-associated compulsivity. Here, we developed an EAB modification (EABM) protocol and examined whether modifying EABs via cognitive training would alter neurocognitive aspects of addiction-associated compulsivity in IGD. We recruited 90 IGD participants who were randomly assigned to receive EABM or sham training in a 1:1 ratio (clinicaltrials.gov identifier: NCT04068064). The EABM intervention involved six consecutive days of exposure to negative emotional terms linked to gaming stimuli and positive terms linked to non-gaming healthy-alternative stimuli. The sham training involved similar stimuli linked to neutral words. Participants underwent event-related functional MRI while performing a regulation-of-craving task and received several behavioural assessments pretraining and post-training. Primary efficacy measures were changes in gaming-related positive EABs, and compulsive gaming thoughts and behaviours. Behaviourally, EABM (versus sham) training decreased gaming-related positive EABs and compulsive gaming thoughts and behaviours. Neurally, EABM training involved decreased activation in the bilateral dorsal striatum in the regulation-of-craving task and altered left dorsal striatum-centric functional connectivity with ventral prefrontal cortical regions, which correlated with decreases in gaming-related EABs or compulsive gaming thoughts and behaviours. EABM training also implicated activation changes in the right medial frontal gyrus and posterior insula. EABM may reduce compulsive gaming thoughts and behaviours via reshaping functional organization of frontostriatal pathways and insular activity in IGD. The therapeutic potential of EABM should be examined in larger, longer-term studies, as should its application to other addictive disorders.

Angiotensin II-induced miR-31-5p upregulation promotes vascular smooth muscle cell proliferation and migration.

Angiotensin II (Ang II) plays a central role in vascular smooth muscle cell (VSMC) proliferation and migration, being key to regulate vascular function and promote vascular remodeling in cardiovascular diseases. We recently showed that miR-31-5p promoted oxidative stress in spontaneously hypertensive rats. In this study, we aim to investigate whether miR-31-5p and fibronectin type III domain-containing 5 (FNDC5) contribute to Ang II-induced VSMC proliferation and migration. Experiments were performed in primary VSMCs of wide-type (WT) and FNDC5-/- mice as well as the rat A7r5 cell line. We found that Ang II increased miR-31-5p level, reduced FNDC5 expression and stimulated VSMC proliferation and migration, which were aggravated by miR-31-5p mimic, and prevented by miR-31-5p inhibitor in VSMCs. The Ang II-induced VSMC proliferation were prevented by exogenous FNDC5 in both WT and FNDC5-/- mice, while the effects were more significant in FNDC5-/- mice. Furthermore, exogenous FNDC5 reversed the effects of miR-31-5p mimic on VSMC proliferation and migration in Ang II-treated VSMCs. Meanwhile, FNDC5 deficiency prevented the effects of miR-31-5p inhibitor on VSMC proliferation and migration in Ang II-treated VSMCs. In conclusion, our findings demonstrate that the miR-31-5p upregulation and the following FNDC5 downregulation contribute to Ang II-induced VSMC proliferation and migration.

Checkerboard corner detection method based on neighborhood linear fitting.

To improve the calibration accuracy of a vision measurement system, a checkerboard corner detection method based on linear fitting of the checkerboard local contour is proposed. First, by binarization and morphological dilation of the checkerboard image, the coordinates of two adjacent vertices of adjacent dark squares are obtained; the midpoint of the two vertices is taken as the reference point; the reference dotted array is obtained; and the Zernike moment subpixel method is used to obtain the checkerboard contour data points in the neighborhood of each reference point. Finally, the contour points are classified according to the orientation based on the reference points; two intersecting lines are fitted; and the intersection of the two lines is exactly the corner point that we want to find. A camera calibration experiment was conducted on the same group of checkerboard images. The results show that the calibration results of the corner points obtained based on this method are highly consistent with the OpenCV library function method and the MATLAB Toolbox calibration method, and the reprojection error is smaller. At the same time, it is robust to changes in the light source brightness.

Characterization of a novel arsenite long-distance transporter from arsenic hyperaccumulator fern Pteris vittata.

Pteris vittata is an arsenic (As) hyperaccumulator that can accumulate several thousand mg As kg-1 DW in aboveground biomass. A key factor for its hyperaccumulation ability is its highly efficient As long-distance translocation system. However, the underlying molecular mechanisms remain unknown. We isolated PvAsE1 through the full-length cDNA over-expression library of P. vittata and characterized it through a yeast system, RNAi gametophytes and sporophytes, subcellular-location and in situ hybridization. Phylogenomic analysis was conducted to estimate the appearance time of PvAsE1. PvAsE1 was a plasma membrane-oriented arsenite (AsIII) effluxer. The silencing of PvAsE1 reduced AsIII long-distance translocation in P. vittata sporophytes. PvAsE1 was structurally similar to solute carrier (SLC)13 proteins. Its transcripts could be observed in parenchyma cells surrounding the xylem of roots. The appearance time was estimated at c. 52.7 Ma. PvAsE1 was a previously uncharacterized SLC13-like AsIII effluxer, which may contribute to AsIII long-distance translocation via xylem loading. PvAsE1 appeared late in fern evolution and might be an adaptive subject to the selection pressure at the Cretaceaou-Paleogene boundary. The identification of PvAsE1 provides clues for revealing the special As hyperaccumulation characteristics of P. vittata.

COVID-19 vaccination for patients with benign childhood epilepsy with centrotemporal spikes.

AIM: There is a high demand for information on COVID-19 vaccination for patients with childhood epilepsy with centrotemporal spikes (BECTS). Patients with this condition need a stable, daily life; unfortunately, the decision of vaccination is not easy for their parents. We evaluated patients with BECTS for symptoms and seizure control after COVID-19 vaccination. METHODS: We asked the caregivers of all patients who visited our hospital to report their vaccination status, and if vaccinated, their experience in terms of adverse effects and seizure control after the second dose of the four Chinese-approved COVID-19 vaccines. RESULTS: Seventy-seven children had received their second COVID-19 vaccine dose: 58 of 77 (75.3%) received Sinopharm (Beijing): BBIBP-CorV (Vero cells) and 16 (20.8%) received CanSino: Ad5-nCoV. Twenty of seventy-seven (25.97%) patients with BECTS reported having side effects; all effects were mild that could be relieved themselves. For Sinopharm (Beijing): BBIBP-CorV (Vero cells), the most frequent local side effect reported by the parents was pain at the site of injection (17.24%) and systematic side effect was fatigue (15.52%). For CanSino: Ad5-nCoV, the most reported local side effect was pain at the site of injection (6.25%). All parents reported that their child's side effects could be relieved by themselves. No patient reported status epilepticus or exacerbation of a pre-existing condition. If non-vaccinated, the cause of hesitation was explored: 40% of parents worried about inducing seizures, 19% of parents worried about vaccine side effects, 32% of parents worried about the vaccine-antiepileptic drug interactions, and 9% of parents feared for their child's physical condition. More than 34.1% of parents accepted that the decision to get the vaccine for their child was difficult. Over 90% of parents believe that research on the safety and tolerability of vaccination would help them to make the decision. CONCLUSION: Our data suggest that COVID-19 vaccination is well tolerated and safe in patients below 18 years of age having BECTS, thereby supporting the recommendation of vaccination.

Differences in cognition, short-chain fatty acids and related metabolites in pregnant versus non-pregnant women: a cross-sectional study.

BACKGROUND: Pregnancy induces cognitive reorganization which can lead to mental disorders. The aim of this study is to determine differences in cognitive scores, short-chain fatty acids (SCFAs) and related metabolites between pregnant and non-pregnant participants. METHODS: This cross-sectional study included 67 full-term pregnant women and 31 non-pregnant women. We compared scores of mental state and cognitive assessment tests, as well as serum concentrations of SCFAs, hormones, inflammatory factors, and neurotransmitters between these groups. RESULTS: Scores for information processing speed, immediate visual memory, motor response speed and accuracy, execution ability and verbal use ability in the pregnant group were lower than those in the non-pregnant group (p < 0.05 for all tests). Total serum SCFAs in the pregnant group were significantly lower than those in the non-pregnant group (P = 0.031). Among them, acetate and propionate were significantly decreased (P = 0.013 and 0.037, respectively) whereas butyrate was significantly increased (P = 0.035). Serum peptide YY, glucagon-like peptide-1, γ-aminobutyric acid, and dopamine showed no differences between the two groups. However, cortisol, adrenocorticotropic hormone, and acetylcholine were significantly increased in the pregnant group as compared with the non-pregnant group (P = 0.039, 0.016, and 0.012, respectively). Tumor necrosis factor-α was increased and interleukin-10 significantly decreased in the pregnant group (P = 0.045 and 0.019, respectively). CONCLUSION: According to our study findings, cognitive reorganization in the third trimester of pregnancy showed that both the passive storage capacity of working memory and the executive function of online information processing were decreased to varying degrees. At the same time, the changes in total SCFAs, the proportions of SCFAs and related metabolites were also detected. These changes in the internal environment may be increasing the risk of perinatal mental illness.

Multihydrophone Fusion Network for Modulation Recognition.

Deep learning (DL)-based modulation recognition methods of underwater acoustic communication signals are mostly applied to a single hydrophone reception scenario. In this paper, we propose a novel end-to-end multihydrophone fusion network (MHFNet) for multisensory reception scenarios. MHFNet consists of a feature extraction module and a fusion module. The feature extraction module extracts the features of the signals received by the multiple hydrophones. Then, through the neural network, the fusion module fuses and classifies the features of the multiple signals. MHFNet takes full advantage of neural networks and multihydrophone reception to effectively fuse signal features for realizing improved modulation recognition performance. Experimental results on simulation and practical data show that MHFNet is superior to other fusion methods. The classification accuracy is improved by about 16%.

Robust Mesh Segmentation Using Feature-Aware Region Fusion.

This paper introduces a simple but powerful segmentation algorithm for 3D meshes. Our algorithm consists of two stages: over-segmentation and region fusion. In the first stage, adaptive space partition is applied to perform over-segmentation, which is very efficient. In the second stage, we define a new intra-region difference, inter-region difference, and fusion condition with the help of various shape features and propose an iterative region fusion method. As the region fusion process is feature aware, our algorithm can deal with complex 3D meshes robustly. Massive qualitative and quantitative experiments also validate the advantages of the proposed algorithm.

Environment-friendly bio-based controlled-release phosphate fertilizer with waste kitchen oil as coating material: Preparation, characterization, and mechanisms.

Recently, Bio-based polyurethane controlled-release fertilizers (BPCF) have been developed rapidly owing to their environmental friendliness, renewability, and low cost. However, the unsatisfying controlled release prohibits their large-scale direct application in agricultural production. Here, we prepared bio-based controlled-release phosphate (P) fertilizers using harmful waste kitchen oils (WKO) as coating materials. The membrane shell surface was modified with multi-walled carbon nanotubes (CNT), and superhydrophobic controlled-release phosphorus fertilizers (SCRF) were obtained. After CNT modification, the controlled release period of SCRF was greatly improved. Phosphorus released period of SCRF reached over 67 d while that of BPCF was merely ∼49 d. Additionally, the surface energy, cracks, roughness, microstructure, cross-linking degree, etc., of the membrane shells were measured. The results showed that CNT greatly improved the hydrophobic properties of the membrane shells. The findings indicated the application of modified WKO with great agricultural value in preparing environment-friendly BPCFs.

Design, Catalyst-Free Synthesis of New Novel α-Trifluoromethylated Tertiary Alcohols Bearing Coumarins as Potential Antifungal Agents.

A new method for the synthesis of α-trifluoromethylated tertiary alcohols bearing coumarins is described. The reaction of 3-(trifluoroacetyl)coumarin and pyrrole provided the target compounds with high yields under catalyst-free, mild conditions. The crystal structure of compound 3fa was investigated by X-ray diffraction analysis. The biological activities, such as in vitro antifungal activity of the α-trifluoromethylated tertiary alcohols against Fusarium graminearum, Fusarium oxysporum, Fusarium moniliforme, Rhizoctonia solani Kuhn, and Phytophthora parasitica var nicotianae, were investigated. The bioassay results indicated that compounds 3ad, 3gd, and 3hd showed broad-spectrum antifungal activity in vitro. Compound 3cd exhibited excellent fungicidal activity against Rhizoctonia solani Kuhn, with an EC50 value of 10.9 µg/mL, which was comparable to that of commercial fungicidal triadimefon (EC50 = 6.1 µg/mL). Furthermore, molecular docking study suggested that 3cd had high binding affinities with 1W9U, like argifin.

Synthesis of Novel Indole Schiff Base Compounds and Their Antifungal Activities.

A series of novel indole Schiff base derivatives (2a-2t) containing a 1,3,4-thiadiazole scaffold modified with a thioether group were synthesized, and their structures were confirmed using FT-IR, 1H NMR, 13C NMR, and HR-MS. In addition, the antifungal activity of synthesized indole derivatives was investigated against Fusarium graminearum (F. graminearum), Fusarium oxysporum (F. oxysporum), Fusariummoniliforme (F.moniliforme), Curvularia lunata (C. lunata), and Phytophthora parasitica var. nicotiana (P. p. var. nicotianae) using the mycelium growth rate method. Among the synthesized indole derivatives, compound 2j showed the highest inhibition rates of 100%, 95.7%, 89%, and 76.5% at a concentration of 500 µg/mL against F. graminearum, F. oxysporum, F.moniliforme, and P. p. var. nicotianae, respectively. Similarly, compounds 2j and 2q exhibited higher inhibition rates of 81.9% and 83.7% at a concentration of 500 µg/mL against C. lunata. In addition, compound 2j has been recognized as a potential compound for further investigation in the field of fungicides.

Vortex coagulation treatment of oilfield wastewater.

In this study, the traditional coagulation process was optimized and a method of vortex coagulation for wastewater treatment was proposed for the first time. The process discards the sedimentation method used in traditional coagulation and uses agitation to bring flocs up. These flocs can then be stuck by the filter cotton fixed in wastewater, and the filter cotton and flocs can act as net capturing several times under the action of agitation. It is worth noting that the filter cotton and flocs can synergistically adsorb the suspended and organic pollutants from wastewater. The results showed that the chemical oxygen demand (COD) removal of vortex coagulation could reach 82%, which was 10% higher than that of the traditional coagulation under the same coagulant dosing. In addition, the flocs in conventional coagulation and vortex coagulation were analyzed by IR spectroscopy and XRD, which showed that the mixing process did not destroy the chemical structure of the flocs. Compared with the conventional method, this process does not require a sedimentation tank, which can avoid the investment of equipment construction in this area. The effects of coagulant dosage, pH, stirring speed, and stirring time on the wastewater treatment effects were explored in the experiment.

[Therapeutic effect of Shengjiang Powder on experimental autoimmune encephalomyelitis mice through IL-6/JAK2/STAT3 signaling pathway:based on HPLC].

A high performance liquid chromatography(HPLC) method was established to analyze the components in Shengjiang Powder(SJP) such as emodin and curcumin and explore its therapeutic effect on experimental autoimmune encephalomyelitis(EAE) mice. To be specific, HPLC was performed to determine the content of compounds in SJP such as emodin and curcumin. A total of 72 female SPF C57 BL/6 mice were randomized into control group(equivalent volume of ultrapure water, ig), model group(equivalent volume of ultrapure water, ig), low-, medium-, and high-dose SJP groups(SJP, ig), and positive control group(prednisone acetate, ig), 12 each group. EAE was induced in mice except the control group. Administration began from the first day after immunization. The general conditions, symptom score, and body weight of the mice were recorded. On the 21 st day, mouse brain tissues were separrated. Then hematoxylin-eosin(HE) staining and Luxol Fast Blue(LFB) staining were used to detect the pathological changes of brain tissues. Immunohistochemistry(IHC) was employed to determine the myelin basic protein(MBP) level, and Western blot the expression of occludin and claudin-5, as well as the levels of interleukin-6(IL-6) and proteins in the Janus kinase 2(JAK2)/signal transducer and activator of transcription 3(STAT3) pathway and their phosphorylation levels. The mRNA expression of IL-6, JAK2, and STAT3 was detected by real-time quantitative polymerase chain reaction(qPCR). Finally, molecular docking of six main active components in SJP, including emodin and curcumin, with IL-6, JAK2 and STAT3 was performed, and the binding affinity was evaluated. The results showed that the established HPLC method demonstrated high precision, reproducibility, stability, and high recovery of samples. Compared with the model group, SJP reduced the clinical symptom score and alleviate the inflammatory infiltration of brain white matter and demyelination of EAE mice. At the same time, SJP increased the expression of occludin and claudin-5, down-regulated the mRNA expression of IL-6, JAK2, and STAT3, as well as the levels of IL-6/JAK/STAT3 proteins and the phosphorylation levels, with significant difference. Molecular docking suggested that the six active components in SJP had high binding energy with IL-6, JAK2, and STAT3 proteins. The established HPLC method is simple, accurate, and highly sensitive, which can simultaneously determine the content of emodin and curcumin in SJP. SJP may alleviate the clinical symptoms of EAE by inhibiting IL-6/JAK2/STAT3 signaling pathway, protecting the blood-brain barrier, and relieving the inflammatory response and demyelinization of brain tissue.

Urine proteomics identifies biomarkers for diabetic kidney disease at different stages.

BACKGROUND: Type 2 diabetic kidney disease is the most common cause of chronic kidney diseases (CKD) and end-stage renal diseases (ESRD). Although kidney biopsy is considered as the 'gold standard' for diabetic kidney disease (DKD) diagnosis, it is an invasive procedure, and the diagnosis can be influenced by sampling bias and personal judgement. It is desirable to establish a non-invasive procedure that can complement kidney biopsy in diagnosis and tracking the DKD progress. METHODS: In this cross-sectional study, we collected 252 urine samples, including 134 uncomplicated diabetes, 65 DKD, 40 CKD without diabetes and 13 follow-up diabetic samples, and analyzed the urine proteomes with liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS). We built logistic regression models to distinguish uncomplicated diabetes, DKD and other CKDs. RESULTS: We quantified 559 ± 202 gene products (GPs) (Mean ± SD) on a single sample and 2946 GPs in total. Based on logistic regression models, DKD patients could be differentiated from the uncomplicated diabetic patients with 2 urinary proteins (AUC = 0.928), and the stage 3 (DKD3) and stage 4 (DKD4) DKD patients with 3 urinary proteins (AUC = 0.949). These results were validated in an independent dataset. Finally, a 4-protein classifier identified putative pre-DKD3 patients, who showed DKD3 proteomic features but were not diagnosed by clinical standards. Follow-up studies on 11 patients indicated that 2 putative pre-DKD patients have progressed to DKD3. CONCLUSIONS: Our study demonstrated the potential for urinary proteomics as a noninvasive method for DKD diagnosis and identifying high-risk patients for progression monitoring.

Efficacy of single-session transcranial direct current stimulation on addiction-related inhibitory control and craving: a randomized trial in males with Internet gaming disorder.

BACKGROUND: Transcranial direct current stimulation (tDCS) of the dorsolateral prefrontal cortex (dlPFC) may reduce substance use and other addictive behaviours. However, the cognitive mechanisms that underpin such effects remain unclear. Impaired inhibitory control linked to hypoactivation of the prefrontal cortex may allow craving-related motivations to lead to compulsive addictive behaviours. However, very few studies have examined whether increasing the activation of the dlPFC via anodal tDCS could enhance inhibitory control over addiction-related distractors. The current study aimed to enrich empirical evidence related to this issue. METHODS: Thirty-three males with Internet gaming disorder underwent active (1.5 mA for 20 minutes) and sham tDCS 1 week apart, in randomized order. We assessed inhibitory control over gaming-related distractors and craving pre- and post-stimulation. RESULTS: Relative to sham treatment, active tDCS reduced interference from gaming-related (versus non-gaming) distractors and attenuated background craving, but did not affect cue-induced craving. LIMITATIONS: This study was limited by its relatively small sample size and the fact that it lacked assessments of tDCS effects on addictive behaviour. Future tDCS studies with multiple sessions in larger samples are warranted to examine the effects on addictive behaviours of alterations in addiction-related inhibitory control. CONCLUSION: These findings demonstrate that stimulation of the dlPFC influences inhibitory control over addiction-related cues and addiction-related motivation. This is the first empirical study to suggest that enhanced inhibitory control may be a cognitive mechanism underlying the effects of tDCS on addictions like Internet gaming disorder. Our finding of attenuated background craving replicated previous tDCS studies. Intriguingly, our finding of distinct tDCS effects on 2 forms of craving suggests that they may have disparate underlying mechanisms or differential sensitivity to tDCS. CLINICAL TRIALS #: NCT03352973.

Resting-state connectome-based support-vector-machine predictive modeling of internet gaming disorder.

Internet gaming disorder (IGD), a worldwide mental health issue, has been widely studied using neuroimaging techniques during the last decade. Although dysfunctions in resting-state functional connectivity have been reported in IGD, mapping relationships from abnormal connectivity patterns to behavioral measures have not been fully investigated. Connectome-based predictive modeling (CPM)-a recently developed machine-learning approach-has been used to examine potential neural mechanisms in addictions and other psychiatric disorders. To identify the resting-state connections associated with IGD, we modified the CPM approach by replacing its core learning algorithm with a support vector machine. Resting-state functional magnetic resonance imaging (fMRI) data were acquired in 72 individuals with IGD and 41 healthy comparison participants. The modified CPM was conducted with respect to classification and regression. A comparison of whole-brain and network-based analyses showed that the default-mode network (DMN) is the most informative network in predicting IGD both in classification (individual identification accuracy = 78.76%) and regression (correspondence between predicted and actual psychometric scale score: r = 0.44, P < 0.001). To facilitate the characterization of the aberrant resting-state activity in the DMN, the identified networks have been mapped into a three-subsystem division of the DMN. Results suggest that individual differences in DMN function at rest could advance our understanding of IGD and variability in disorder etiology and intervention outcomes.

Cavity Enhanced Multi-Channels Gases Raman Spectrometer.

Raman spectroscopy has the advantages of multi-component detection, with a simple device and wide concentration ranges, and it has been applied in environmental monitoring and gas logging. However, its low sensitivity has limited its further applications. In fact, the Raman signal is not weak, but the utilization efficiency of the Raman signal is low, and most of the signal is wasted. Given this, in this paper we report a cavity-enhanced multi-channel gas Raman spectrometer with an eight-sided cuvette. First, we simulated the Raman scattering intensity at angles from 30 degrees to 150 degrees. The simulation results showed that the signal intensity at an angle of 45° is 1.4 times that observed at 90°. Based on the simulation results, we designed a three-channel sample cell for higher sensitivity. The results of these experiments showed that the sensitivity could be increased by adding all signal together, and the limit of detection (LOD) for CO2 was 75 ppm, which is better than that of each channel. This paper thus presents a new method to enhance the Raman signal, which can be used in field applications.

High-Sensitivity Raman Gas Probe for In Situ Multi-Component Gas Detection.

Multiple reflection has been proven to be an effective method to enhance the gas detection sensitivity of Raman spectroscopy, while Raman gas probes based on the multiple reflection principle have been rarely reported on. In this paper, a multi-reflection, cavity enhanced Raman spectroscopy (CERS) probe was developed and used for in situ multi-component gas detection. Owing to signal transmission through optical fibers and the miniaturization of multi-reflection cavity, the CERS probe exhibited the advantages of in situ detection and higher detection sensitivity. Compared with the conventional, backscattering Raman layout, the CERS probe showed a better performance for the detection of weak signals with a relatively lower background. According to the 3σ criteria, the detection limits of this CERS probe for methane, hydrogen, carbon dioxide and water vapor are calculated to be 44.5 ppm, 192.9 ppm, 317.5 ppm and 0.67%, respectively. The results presented the development of this CERS probe as having great potential to provide a new method for industrial, multi-component online gas detection.